1. Field of the Invention
The present invention relates to a novel thermoplastic and organic solvent-soluble poly(amide-imide) elastomer and the process for producing the same.
2. Description of the Prior Art:
The demand for elastomer having an excellent heat resistance is recently increasing for many fields of industrial uses.
Polyimide and poly(amide-imide) are well known as an excellent heat resistant resin and are ordinarily prepared by a two-step process, in which the first step is accomplished by reacting a tetracarboxylic acid dianhydride or a tricarboxylic acid anhydride monohalide with a nitrogen containing compound having active hydrogens, such as diamino compound or dicarboxylic acid dihydrazide, to obtain a polyamic acid as a precursor, and the second step is accomplished by treating the resulting precursor with a dehydrating agent, such as a mixture of acetic acid anhydride and pyridine, or by heating the precursor to convert the polyamic acid to the cyclic polyimide. However, the resulting heat resistant polyimide or poly(amide-imide) is insoluble in organic solvents and cannot be casted into shaped articles. Moreover, it has never been used as elastomeric materials for the lack of elastomeric properties. In one example of the use of conventional heat resistant polyimide or poly(amide-imide) as film or coating materials, a precursor, that is an organic solvent-soluble polyamic acid is casted into film or coated on the object, thereafter these films or coating is subjected to dehydration and ring-closure reactions at high temperature to obtain infusible, organic solvent-insoluble and rigid polyimide or poly(amide-imide) film.
The inventors succeeded to produce a novel thermoplastic and organic solvent-soluble poly(amide-imide) elastomer by a novel one-step process using an acid anhydride functional polymer under restricted conditions.